Crossover tools are used in conjunction with isolation packers to allow gravel packing and frac packing (hydraulic fracturing in conjunction with gravel packing). Some designs are run in already positioned to allow fluids pumped through the string to crossover into an annular space outside the screen assembly and to take fluid returns through a wash pipe inside the screens. The returns go back through a discrete path in the crossover and exit into the annular space above the packer.
Another type of crossover is shifted between squeeze and circulate positions by moving it relatively to the seal bores in the packer body. These designs shown in FIGS. 1 and 2 involve putting the tool into a supported position at discrete axially spaced locations using spaced indicating subs and complex collet designs known in the industry as SMART® collets. FIG. 1 shows this type of design. A packer 10 has a seal bore 11, slips 12 and a sealing element 14. It has a seal bore 18 in an extension assembly below it. It also features spaced single indicating sub 20 and double indicating sub 22. At the bottom are the screen sections depicted schematically as 24. The crossover tool assembly 26 is connected at top end 28 to a string that can be manipulated from the surface. Passage 30 is open at ports 31 and 32 for delivery of fracturing fluid to the annular space below packer 10 while return passage 34 is closed at outlet 36 by virtue of seals 35 and 37 sealing in packer bore 11. An initial threaded connection 38 for run in can be undone when the assembly is properly paced and after packer 10 is set. Below the crossover tool 26 is a shifting tool 40 to selectively close sleeve 41 to isolate port 32 when crossover assembly 26 is retrieved from the well. The SMART® collet 42 is below the shifting tool 40 and below that tool is an indicating collet 44 that comes into play during the evacuation position when collet 44 comes up against the bottom of indicating sub 22 and the ports 16 come up above seal bore 18. A j-slot mechanism (not shown) is operative after threaded connection 38 is undone. It can un-support the SMART® collet 42 so that it can clear the indicating sub 22 and be set down on top to define the circulating position shown in FIG. 2. In this position port 36 is open, the SMART® collet 42 is on top of indicating sub 22 and ports 16 are still in seal bore 18. Some of these components and how they operate can be seen in U.S. Pat. No. 6,464,006 FIG. 3.
There are many external seals in the design of FIGS. 1 and 2 and they can be prone to sticking. Another issue with this design especially in very deep wells is that it is difficult to know if the applied pickup force at the surface has translated into a sufficient pickup force at the crossover 26 to have lifted the SMART® collet 42 high enough so that when weight is set down again it will land in the FIG. 2 position. Frequently, the tool position has to be confirmed with an effort to circulate or reverse circulate to be sure the tool has actually obtained the circulation position. Using spaced indicating subs to define the various positions makes for a longer assembly that adds cost and decreased ability to maneuver the assembly in highly deviated wellbores.
Instead of setting down for support below the packer 10 the present invention rests the tool assembly above. It doesn't rely on lifting seals into or out of contact with the packer body to attain the circulating position. Instead, with the crossover supported above the packer a j-slot assembly moves parts relatively within the crossover tool itself to open or close the return path to define the circulation and squeeze positions respectively. The assembly is shorter and expensive parts used for support of the tool in the packer are eliminated. The tool can reliably move back and forth between the squeeze and circulating positions with a simple short pickup and set down movement. Using set down weight on top of the packer directly counters the high pressure forces generated when doing the squeezing than what could be obtained with the FIGS. 1 and 2 designs. These and other aspects of the present invention will become more apparent to those skilled in the art from a review of the description of the preferred embodiment and the associated drawings that appear below while recognizing that the full scope of the invention is to be determined by the appended claims.